1. Field of Invention
The invention relates to optical devices and, in particular, to windows for optical scanning devices and methods of manufacturing optical scanner windows.
2. Discussion of Related Art
Optical scanning devices, or optical readers, are widely used throughout commerce and include products such as retail checkout scanners and inventory control systems. Typically, a scanner is used to read encoded data such as a printed bar code. The data may include information regarding, for example, manufacturer, product and price. In the most common applications, the scanner illuminates the barcode with light and reads reflected light off of the barcode. After reading the code from a product or label, a database can be accessed to obtain product information and to record the scanning event for use in, for example, inventory, accounting, marketing, etc.
Most modern scanning devices use a laser beam, typically produced by laser diodes, to provide a focused, collimated light that can be quickly scanned across a barcode. The use of a laser can improve reading ability and reading accuracy at a distance and with non-planar barcodes. Using a device such as one or more mirrors, the laser light can be scanned in multiple directions at high frequency to capture barcodes regardless of the barcode orientation in relationship to the scanner. This means that the barcode need not be aligned in any particular direction to be accurately scanned. Scanners may be handheld or stationary (e.g., fixed mount scanners), and to facilitate reading, the scanner may be moved to the product or the product may be moved to the scanner.
Scanners typically include a window separating the optical components of the scanner from the scanning area. Although a product code need not come in contact with the window in order to read the code, the product package and scanner window often contact each other during the scanning process. Because scratches on the surface of the scanner window may lead to inaccurate or nonfunctional scans, the external surface of a scanner window is often coated or covered with a material that is more scratch resistant than glass.